The ability to create three-dimensional (3D) models of brain tissue from patient-derived
cells, would open new possibilities in studying the neuropathology of disorders such
as epilepsy and schizophrenia. While organoid culture has provided impressive examples
of patient-specific models, the generation of organised 3D structures remains a challenge.
3D bioprinting is a rapidly developing technology where living cells, encapsulated
in suitable bioink matrices, are printed to form 3D structures. 3D bioprinting may
provide the capability to organise neuronal populations in 3D, through layer-by-layer
deposition, and thereby recapitulate the complexity of neural tissue. However, printing
neuron cells raises particular challenges since the biomaterial environment must be
of appropriate softness to allow for the neurite extension, properties which are anathema
to building self-supporting 3D structures. Here, we review the topic of 3D bioprinting
of neurons, including critical discussions of hardware and bio-ink formulation requirements.